Electron discharge device and associated circuits



Aug. 14, 1951 E. w. HEROLD 2,564,053

ELEcTRoN DISCHARGE DEVICES AND ASSOCIATED CIRCUITS Filed May 5o, 1945 e sheets-sheet 1 /.f. narrar IN V EN TOR.

y.. jij@ Aug. 14, 1951 E. w. HERQLD 2,564,063

ELECTRON DISCHARGE DEVICES AND ASSOCIATED CIRCUITS Filed May 50, 1945 6 Sheets-Sheet 2 caf/fiar mmm/4:2 j

HWK/766 77?/7/1/560/1/006' TMF rra/wir Aug- 14, 1951 E. w. HEROLD 2,564,063

ELECTRON DISCHARGE DEVICES AND ASSOCIATED CIRCUITS Aug. 14, 1951 E. w. HEROLD 2,554,053

ELECTRON DISCHARGE DEVICES AND ASSOCIATED CIRCUITS @www E. W. HEROLD Aug. 14, 1951 6 Sheets-Shea?l 5 Filed May 30, 1945 a U M M f W 0 P M w A w j f f E M U MA M 6 0 EL f HN 66% pn f W UM@ V W A m A uw @uw W Uw? V w A m F W/MJ. v 5 n W w SN SNA@ www@ N? QN L .Hlilf .NM1 I. ||I| |||L f/ xwkuwr k bk f Skkm j?? J l? I Aug. 14, 1951 E. w. HEROLD 2,564,063

A ELECTRON DISCHARGE DEVICES ANDASSOCIATED CIRCUITS Filed May 30, 1945 6 Sheets-Sheet 6 IN V EN TOR.

iatented ug. 121,v 1`95 Nrrse s Acres ELECTRON DISCHARGE DEVICE AND Assoomtrnncmounrs Edward W. *HerolcL Kingston, N. J., assignpr ,t0 Radio Corporationnf America, aorncrationefi Delaware Application May so, 1945, serialNo. 596,755

22 ,Claims- My invention relates to electron discharge .de- Vicesand associated circuits andmore particularly to electron discharge devices of Vthekindutilizing a beam of electrons which is periodically deflected, and circuit means for automatically y maintaining the beam centered.

One type of conventional beam deiection tube described and claimed -in my United States -Paten tNo. 2,294,659 assigned to the same assignee as jthe `aperture assembly andthe deecting electrodes which form an electronlens. Alternating -`volt1age applied to the ydeflecting electrodes .will `cause periodic deflection of the-beam across the intrcepting wire to vthe output electrode. In normal operation A-thelincoming .signal `and local "oscillator voltages are impressed simultaneously across the d-eiiection electrodes usually by means of ahigh frequencyresonant-line circuit. An/inf termediate vfrequency transformer is connected to `-Athe output electrode. Y Best `mixer .operation re.- duires-the -beam to-be accurately centered on .the intercepting Wire. A'-I'hisisdone vby va bias .voltage "applied to the deflecting electrodes.

It has beenfound-thatwviththis.type of tube the .most critical operating voltage is .the beam centering bias. -It has .also Ybeen Afound .thattubes which `have Athe best vsignal-to-.noise ratio are usually the most critical '.to adjust. As a.result, 'it lhas -been-necessaryato.provide a frontof panel bias control onequipmentusing this .type of tube sovthat small changes in voltageor small changes Lin-tube characteristics during .theflife would Anot :cause .toomuch drop in performance. The ad- -iustment ordinarily Ymust lbe made withanactual signalpresent since the `anodec-urrent does not vary enough to `permitthe Ybest operating-.point to-be found by using ameter in the anode.

-Itistherefore the -principal objectof my inven- :tion to provid-e van electron discharge device of `therbeam deflection type .inwhich -the most .crit icaloperatingvoltag'e can vbe maintained automatically at `substantially the correct value. More speciiically, itis anobject of Amy invention -to provide yan'electrondischarge device of the beam deflection -type and an .associated circuit Y r.1! -in which thebeam isautomatically properly cen- ..tered.

The novel .features which I believe to be char.- acteristicof my inventionare set forth With p articularity .in tbeappended claims, but the inven- .tion .itself 4will .best .be understeod by reference@ .the Kellogg/,ins descri taken Ain Connection `v /th theacerppaprll agrar/ine ,in which .Figure l sascliemati-diaeram .Showing .ahem deflection.tubeOmmeland.uriderpsieeraion and its eeeeeiated Q uit- Fieiire .2 and 3 ,are graphs ehewing 9eige#.marea-@risticii f e probeer' .ctere@ .beam and imerleprlr @entered beam- Ejigure fl .is afchematic diagram of one "form of device made ac ordi invention'and its vFigurel 1 A:and a 'modified circuit',Y made according to'my invention Ior main aining the beam auto'- matically centered. Figure "8' lshows va series of curves showingy foperationof the device and circuit shownin Figures?. `Figure9 is a modification of the arrangement Yshown'i'n'ligure '7. Figure 10 is v`a graph showingoperation ofthe tube and circuit'of Figure 9. '.Figure'll is a' still further modi-iflcation of theA tube and circuit shown in Figure 577. -`Figure-124s a graph showing the operation of lthe tubeand circuit shown in' Figure 11.` Figures -1Y3.and 14 yare stillfurther modifications of a tube and circuit made rin accordance With my inven- 1on. I v

Referring A-to -Figure 1 of the drawings, the usual '.Ybeamv deflection tube used as a mixer in superheterodyne reception includes an elongated envelope .Illi having lat .one end Jthe lindirectly heated .cathode .I I Tand .at -the other a collector .or-anode I2. :Positionedneim adjacent the cathode is the l. aperture 1assembly .and accelerator .through which v`rthe `.electrons are .directed and which .with .the deflecting electrodes IIl and .I5 provide a lens action .for Lfocusingthe beam on the interceptinglectrode I6. A secondary electron suppressor .-LI is .positioned .between .the in.E tercepter I6 .andthe .anodell Analternating voltage isgappliedito the .deflecting electrodes `I4 and .I5Y by means. .of the;.input circuit AI8, to.which botnthainputsignal voltage Aand the local .oscillatorvoltage maybaapplied. -The intermediate frequency .output 4.t1:ansformm I9 is, connected f to .the outputllelectrode 1,2. .-f'lhedeflecting .volt-` average current is that shown. by the ydotted line 2. The minimum in each'case appears at the correct mixer bias indicated. From the graph it is clear that correct centering 'is approximately at the minimum of the anode current-curve although this minimum is rather broad. A slightly misaligned tube will give aslightly misplaced minimum as shown in Figure 3. l

Because a correctly centered beam' in al well aligned tube passes the same current on one side of the intercepting Wire ason the other, this feature may be used to provide automatic centering With a tube With its associated circuit and in which automatic centering may be had is shown in Figure 4. Like numbers apply to like elements in all of the figures. The tube in Figure 4 differs from that shown in Figure 1 by being provided With a split output electrode .comprising the elements I2 and I2". -Each of these elements is connected to a separate primary 22 and 23 of the intermediate frequency transformer having a secondary 2li.A By-.pass condensers 21 and 28 are also provided. The secondary of the input transformer is split and isolated for different D.C. biasing potentials on electrodes I4 and I5 by means of the condenser 2l. Separate biasing potentials are applied from the biasing voltage source to the' electrodes I4 and I5 through the resistors 25 and 25 which may be manually adjusted.

When the beam is properly centered so that the deflection is equal on both sides of the intercepting electrode I6, the current flowing through each of the resistors 25 and 26 is the same so that the drop across these resistors is the same and no relative change of bias is madeon the deflecting electrodes. If, however, the beam is off-center, more current will flow throughone resistor than the other thus changing the voltage drops and the biasing voltages'. For example, if the beam is off-center upwardly in Figure 4, increased average current will flow on the average to the output electrode element I2 than that to output electrode element( I2" causing a greater drop in resistor 26 than in resistor 25, thus decreasing the positive bias on lelectrode I4 with respect to that on electrode I5 on which the positive bias is increased due tov decreased average current flowing 1throughresistor 2.5. This has the tendency to shift the beam back toward deilectng electrode I5 so thatA the mean positive'. of the beam is again substantially alonga line between the cathode and the intercepting electrode I6 so -that substantially. equal deflections are again produced about the mean path.

A disadvantage ofthe arrangement just described is that a special tube construction is required Which increases the difficulty of manufacture since itinvolves the Iiningupof a second pair of electrodes, I2' and |'2" with the intercepting wire I6. Furthermore, the method'employed involves chiefly current Achanges so that'with an unsymmetrical current characteristic the centering may not be exactly correct for best mixer 4 operations which depends upon the transconductance rather than the current.

Referring to Figure 5 which shows the transconductance characteristic with and without oscillator voltage applied, it is seen that the transconductance, that is the slope of the curves shown in Figure 2, is positive'on one, side of the correct centering and negative onthe other. .A centering system which operates by searching for the point of zero transconductance overcomes the disadvantages listed above and eliminates the necessity kfor a special tube. It has the further advantage that the tube characteristic Which also chiefly determinesmixer operation, that is the transconductance, is the one which is used to correct the centering. In Figure 5 is shown the curves of transconductance plotted against centering bias for the typ-ical tube Whose anode current curves are shown in Figure 2. It is seen that when optimum local oscillator is applied, the average transconductance passes through zero, the correct centering point, with a very high slope thereby providing veryvaccurate centering when this method is utilized. y

One means of deriving automatic centering voltage from the transconductance characteristic requires the application of an auxiliary A.C. voltage to the deflection gplates. The fundamental component of the `A.C. output anode current which results from an A.C. input is zero when the tube is centered, that is, when the transconductance passes through lZero and reverse in phase through this point with equal changes of transconductance in the positive and negative directions. A phase-responsive rectifier operating fromrthe A.C. anode current will supply a direct rcurrent of one polarity when the centering is off on one side and will supply a .direct current of an opposite polarity when the centering is off on the other side. Thisis the action which is needed for incorrect centering. Y

In Figure '7 I show a tube and a circuit made according to my invention which utilizes the transconductance characteristic for providing automatic centeringr of the beam. In this arrangement the bias is provided for deflecting electrodes III and I5 through the resistors 26 Vor 25' and I apply a local oscillator voltage by means of the local oscillator 2'I.vv Connected in output of the tube is a feedback circuit 28 tuned to the localvoscillator frequency. In 4this arrangement the local oscillator voltage is used as the alternating current source for the centering control and the beam deflection tube is utilized as a phaseresponsive rectifier. When thebeam is properly centered, a current having a second harmonic of the local oscillator frequency is generated and there is no fundamental component of local oscillator frequency intheanode circuit, thus circuit 28 whichistunedto the fundamental frequency does notrespond to the current in the output circuit. Thisl circuit 28 discriminating against the strong second harmonic component and having no'voltage across it feeds nothing back to the signal inputy circuit to which it is coupledjAs a result, the normal D.C. anode current flows through resistors 25 and 25' which are arranged to provide deflection plate D.-C. bias. Adjustmentof 26 permits this bias to be varied in either direction. If, now the beam centering is slightly off, that is, toward the upper side of the intercepting electrode I6, there will be a local oscillator frequency component in the anode current which is fed back through the circuit. 28. With the. phase adjustment correctly escrocs' mal local oscllatorevoltage and slightly increase the anode current. /As a result, the D.`C. Ndrop :across the resistors 25^ and 26 will increase, thus decreasing the voltage on electrode I4 and causing the beam to be shifted downwardly and v,so correcting the centering. On the other hand, if the beam has been slightly off toward the lower side of the wire, the local oscillator frequency component in the anode current again appears but in opposite phase. Thus the anodefeedback would also be opposite in phase and wouldbuck the normal local oscillator Voltage. This decreases the anode current and reduces the direct `current voltage drop across 25 andZB -making velectrode L4 more -positive so `as to deflect the beam upward toward the center, thereby again correcting any off-center tendency. vTo explain more detail theraction whichrtakes place, reference is had to Figure 8. In the. upper left-` lhand portion of Figure 8 is shown the output anode current characteristic.anddirectly below this --the'voltage induced in the secondary of the transformer 20 by the local oscillator and the feed.-

zback circuit when the beam is properly centered. v

With the local oscillator Voltage applied, the out- `put current is a formshown by the .solid line and marked 2nd harmonic I output'normal. The result is an average current IR1+R2 marked Normal. If the beam shifts upwardly so that it is off-center and, as shown by the dotted line, Shift up under the .output anode current char.- acteristic, the output current takes the form shown by the dotted line marked, Shiftlupf As `a result, there is a component of output current having a fundamental frequency corresponding to the local oscillator frequency. The local oscillator Acircuit 28 which is tuned to this fundamental frequency then has a voltage induced across it as indicated by the curve EA marked Shift up. This induces a current -in Vthe secondary of transformer 20 in phase with the local oscillator voltage and the resultantl is Vshown as E induced resultant Shift up. v'Ihis -then causes an increase in the output current as indif;

cated by the Shift up average current curve VIal-i-Iaz, causing a drop in voltage across resistors 25' and ZBand a shift down of the beam. On the other hand, if Vthe shift of the beam off-cen- -ter is down, a resultant voltage is generated in v;

circuit 28 corresponding to the voltage curve marked Shift down. It is -observed that the shift is 180 with respect to the shift up of the beam. Under these conditions, the voltageY induced by the circuit 28 and the local oscillator l2'I A,

in the secondary ofthe input transformer 20 buck each .other causing a reduced induced Voltage as shown by the lowermost curves. As a result, the average current in the output-decreases, the voltage drop across the resistors decreases, and the resultant biasing voltage on electrode I4 rises causing the beam to be shifted upward toward Vthe electrode i4. 1

VIf an auxiliary small A.C. is applied to the mixer input using some frequency remote :from the normal signal intermediate frequencysor local Ioscillator frequency, it is also possible to apply automatic centering in a straight-forward manner with a separate phase-,responsive rectifier. In order not to interfere with normal operation the auxiliary A.C. input Amust be small. oSuflcient automatic control is thenobtained by a high rectifier sensitivity. A phase-responsive rectifier circuit suitable for use for this purpose is :disclosed ,in my Patent..2,95.4 .1.2.5 :assigned to Connected across the resistor .higher than cut-off voltage.

the-same assignee as the present application.

Rectiers of the kind described in the patent are essentially mixers which :operate with .the local voscillator at exactly .the same frequencyas the A.C. input giving a .zerotfrequency, that is,

a D..C. routput whose polarity .depends Von the phase of the A.C. input with vrespect to the fixed phase local oscillations.

An automatic centering control using thehigh sensitivity phase-responsive rectifier is shown in Figure 9. In this arrangements. transformer Tl having two secondaries .32 and 33 is utilized for applying a small A.C. potential to -the deflect- Aing electrodes I4 and I5 and for also providing the higher Voltage which must be applied to the phase-responsive rectifier circuit to be described. The biasing voltage is applied from aA Focus adjustmenty source throughvthe resistor 30 the opposite ends of which are 4electrically connected to the deflecting electrodes I4 and I5', being bypassed by condenser 2| for R.F.-currents and bycondenser 3| for currents of 10W frequency. `30 are a pair of tubes V1 and V2 the grids of which are connected to the secondary of transformer T2. The primary of transformer T2 is connected to the out'- put v,electrode I2 through the primary of the in termediate frequency transformer I9. This transformer T2 has its primary tuned to respond to the frequency of the auxiliary low frequency A.C. applied by the transformer T1. An A.,C.

potential is applied between the cathodesan'd' the grids are biased to cut-off, current will not ow unless the grids are raised to a voltage If the voltage applied to the secondary of the transformer T2 is such that the voltage of the grid of the Vtube V1 increases in phase With the Voltage applied to the anode, an increase in current through this `tube `will result, whereas under these conditions the grid of the tube V2 is 'in phase opposition to the anode voltage so that `the current ,through tube V2 decreases if the grid is not biased to Icut-off or, has no effect on this tube if the grid is biased to cut-off. Current therefore flows through resistor .30 to tube V1 causing a drop in voltage on the upper end of resistor `30 and consequently on the deflecting electrode I4.

If the phase ofthe voltage vin the secondary of transformer yT2 is reversed so that tube V2 becomes the conducting. tube, a current will ow in the opposite direction through theresistor 30 lowering the potential at .the lower 4end of the resistor and decreasing the potential on electrode I5. Thus the resultant rectified ,currents can be utilized to control the bias on the deiiecting electrodes. t

No effect is obtained in transformer T2 if the beam is properly centered and Only the second 4harmonic appears in the output electrode I2. Off-centering however will cause an output current component having a frequency .corresponding to the frequency of the voltage applied by transformer T; to electrodes I4 and. I5, and depending upon .the phase. 'eiiherilube V1 .10.1 Y2

accrocs Wi1l.;co`nduct ;tol..bringzaboutf;ar variation; in 'the voltage applied bytransformer'Ti to Lelectrodes .ldfand l lwhen the beam vis properly centered .results in the output current marked fCentered normally. having .a frequency twice` that of the ,auxiliary `low frequency-A.C., with the result that the voltage-output through T2A is zero since fthe hprima-ry is tunedA only to the auxiliary low The difference between the currents of `,tubes V1 and Vg, Iv1V and Ivg-,fis also zero as showrrA If the beam is shifted .upwardly howeverv ais-indicated by the dotted line S l 1iftup,ra current component appearsrin the 'outpu't of thetube of a fundamental frequency which Yenergizesffz and causes the voltage indicated by T2 Shift .upas shown in the curve in Ithe graphs.. If lproperly phased, V1' conducts so thatlanV average? bias. results fas indicated vby @1v1-,LV2 Shiftup causing the upper end of the resistor. 30 to become less positive causing a .less positive bias on electrode I4 and moving the beam back down towardthe other deflecting electrode 1,5110. hrng'about proper centering. On the other hand, ifthe beamI isshifted downwardly .as in dicated by Shift downff the reverse process takes place as indicated by the. Shift down curves shown, the average .bias decreasing on `electrode l5. e .-1 r

In beam deflection tubes of the kindrdescribed above the full output current characteristic includes two Yotherstable points Acorresponding to extreme deflectioneof 'the' beam to either side. Thus, in some cases, it is possible for this auto- Vmatic centering circuit to give so great an out- -put fromfthe -rectifier' that operation is on one `of Vthese incorrect points. f The use of transform- -ers T1 and T2 adds -tothe y'cost ofthefequipment, and hum lmay be an undesirable factor in the operationoftherectifier. .An-improved form of circuit-,whichminimizesthese :objections -is shown. innFiguree-lllh-.cln `this arrangement` the voltage on theeanodes -is fixed Whilefthe voltage. onwtheV cathodes is an alternating voltage appliedfrom `an auxiliary low frequency A.C. -source through thetransformer Ta. Theitubes -iA andNz .may ormayvnotbe operated at cutkoffs.;l The voltagefis applied -to the grids lthrough the tuned v.circuitI 39. tuned .to the auxiliaryk low :frequency A.AC. Lappliedi-to thescathode ofritubes :Viaud V2, Theilow frequency A.C. is applied tonthegfdefiectingfelectrodesethrough the circuit including resistors 31 and 38 and condenser 36 connected in. the :output of the @tube V2 y.which #produces 1 anfA'.-C. -voltage Ea.: acrossv the resistor 38. i ,Eithertube Vi or'ctubeVz conducts' the -greatestcurrentcifd -theibeamis :off centerfand operation is las-described above. n Referr`ing to Figure 12 the` operationof the fph'ase-responsivev rectier circuit andthe center-` ing oircu-itsof- Figure 11"maybefseen inA detail. When properly centered, the normal output current-having -a-irequenc`y tvvicefthat of -the auxf -iliary-lowifrequencyvaction appears but does' not aiectfI-theeinputcircuit l39.- Shift` of the beam up vor'dovvncauses an output having afundamental yfrequency component which Yexcites the input 'circuiti 39 Y and again ifvproperly phased, 'when the beamsl shifted up the current through sothat the relative average biases are asv indilcatedinthe graphsto again properly biasethe -deecting'electrodes to-centerthe beam. Ifthe 'beam `is s hifteddown theopposite action takes place, f c Y `In 'some cases no auxiliary A.C. of low` freiquencyfis read-ily available and it may be desirable to 'generate this A.C. in the rectier .itself', 'by makingA itself-oscillating. A.double trivode .utilizing .a vbalanced modulator oscillator .circuit.,has certain advantages. Such an arrangement is shownin Figure 13. In this arrangement each ofthe tubes V1. and VV2 also functionsasan oscillator being provided :withrdarfeedback coil .45.xand '46 for energizing :theswinding of yTR;connected between the cathodes..H The auxiliary voltage applied to .thedefleeting electrodesis obtained by coupling the coil 4T tothelwinding of TR. In other respects the circuitjs' much the same as those previously described and" functions in substantially the -same mannersA Itis-of course obvious that a 4double f triode or .pair of triodes as wellv as tetrodes orpentodes could be used for the tubes V11and`V2.;'. j. if

"In" Figure 14 I show an arrangement wherein va .singletubeVafis'utilized for bringing about '-automaticfcentering; In this arrangement the automatic centering bias resistor 30 has connected to it a. second resistor 53 connected to ground for establishing aA normally small bias across :pointsfl and62. A separate oscillator 50 is em.- ployed for applying the Aauxiliary A..C. center- .ingfyoltage t0 thedeecting` electrodes by means of thercoil l5l coupledto. the oscillator. A sec- -ondV coil 52iprovides the additional A.C. needed .to...op erate the phase-responsive rectier and is connected to the cathode of V3. Tube V3 is thus connected; toytheoscillator and its plate current, in eiectyflows Vthrough the upper part ofthe resistor -30. Theresstor .53 in effect replaces the second tube usedv in the other arrangements. The *currentY through the resistor 30 splits lthrough the tube Va and the resistor -53 so that normalvvoltages across these resistors .are-equal and opposite. If an A.C. voltage ape .pearsonthe gridof Va,v due Yto improper cen.-

tering of thebeam,lthe current in V3 will change. heuthet:beamasy .shifted up, the. A.:C onerid .giseout of phase Vwith the A.C. on the cathode so. that, the resultant Vcurrent through Vthe* resistor, Sli-,increases so that there is a voltage drop .at thefcupper end-of resistor 30 reducing the bias on the deilecting-electrode .I4 to shift the beam down again.'l`he;=reverse action takesplace if Athe beamisi'oi-centerrin the opposite direction. i While I have indicated the preferred embodimentspf my,invention of which Iam now aware and have also indicated .only one specific appli- .cationfor which mynvention maybe employed, .f-itcfwill4 be" apparent that my invention is by no means limited to the exact forms illustrated or Y; will-increaseand-through V2 decrease'or have 1| pathQ-lean's for applying ay biasing Yrvoltage to said 9i deecting electrodemeans for maintaining said beam alongsaid predetermined path when no deflecting voltagel is applied to said deflecting electrode means, means for applying anv alternating voltage of one frequency tosaid deflecting electrode means to periodically deflect said electrons, and a second means for applying an alternating Voltage of a different frequency to said deflecting electrode means, and means connected to said biasing means and responsivetoa deviation of the electron beam from said predetermined path as a mean position and including means responsive to said second frequency for varying the biasing voltage whereby said beam` is returned to said predetermined path as a mean-position.

2. An electron discharge` device having means including a cathodev for directing a beam of elecn trons along a predetermined path, defiecting-electrode means alongrv the path of said electrons for periodically deecting said electrons fromv said path, and output means in the path ofsaidelec.

trons. for receiving saidelectrons, means for applying a deflecting voltageitosaid defiecting electrode means of a given frequency,- other means for applying a deecting electrode voltage to defleetingY electrode means of a different frequency, means'forapplying a biasing voltage to said. de-

flecting electrode means for maintaining saidbeam directed along said predetermined path when no deecting voltage` is applied to said defiecting electrode means, andmeans responsive to theY output current due to said defiecting voltage of different frequency when said beam d-eviates fromv said predetermined path asa mean position for varying the biasing voltage toreturn said beam to saidprede-terminedr path as a mean posi. tion.

3. An electron discharge device having a cathode for supplying a beam of electronsy along a predetermined path, an. output electrode positioned in the path of said electrons and a pair of defiecting electrodes positioned on opposite sides of said beam path and betweenl said cathode andy output electrode, and an intercepting electrodepositioned between said cathode and output electrode and on which said beam is directed when no deflecting voltage is applied.k tosaid deflecting electrodes, means for applying an alternating voltage of one frequency to said deflecting electrodes for defiecting said electron beam across saidintercepting electrode whereby an output current flows to said. output electrode of a frequency twice that of said one frequency, biasing means for applying a biasing voltage to said deflecting electrodes to maintain said beam directed on said intercepting electrode. when no alternating voltage is applied to saiddeflecting electrodes from said alternating voltage source, and means coupled between said output electrode and said biasing means and responsive to an output current of said one frequencyupon-` deviation of the electron.- beam from said predetermined path as a mean position for returning said beam to said predetermined path as a mean. position` 4. An electron discharge device having means including a cathode for directing an electron beam along a predetermined path, deiiecting electrode means along the path of said electrons for deflecting said electrons from said path, means for applying an alternating voltage of a fundamental frequency to said deecting electrode means for periodically deflecting said beam of electrons about said predetermined path as a mean position, and means. in the path. of said electrons for. providing an output current of twice liOi theI frequency of the applied deecting. voltage when said beam is properlycentered. along saidpredetermined path andan output current hay. ing a fundamental frequency component when the beam is improperly centered along said predeterminedpath, and means coupled, to the means in thepath of said electronsv and. responsive to-an. output current .of the fundamental frequency genr. erated4 when said beam. is unequally deflected. about said meanpositionfor returning saidv beam. to.,- said predetermined path as a mean. position to. providevequal. deflection about said mean position.

5. An electron discharge device having means, including a cathode for, directing an. electroni beam along. a, predetermined path, a4v deecting electrode means positioned! along the p athA of saidl beam. of electrons for deflecting said electrons from; said. path, an. output.. electrode means for receiving saidbeam of electronsm.eans.for app1y-.. ing: an alternating voltage of a. fundamental fre.- quency -to said deflecting electrodes, for periodi. cally deflecting said beam. of electrons on, opposite sides ofv said predetermined path as. a meanr position, said output. electrode means having means for generating currents of only a second harmonic of said fundamental frequency when said beam is properly centered on said output electrode meansand a. component.. 0f the fundar. mental frequency when, said beam isimproperly. centered, and` means. connected to said outputI electrode means and responsive tocu-rrentsof thefundamental frequency, means. for applying. a` biasing voltage to saiddeecting electrode means.. for centering said beam. along. said predetermined.

E path, said meansconnected to said output electrode. means` responding. to. a. fundamental fre.- quency output. when said beamis. deflected un. equally on oppositel sidesl of said predetermined. path, said-4 last meansr varyingy the biasing voltage on said deiiectingt electrode meansy to return. said. beam` to said predetermined. path` asa mean position to. maintain equal. deflection of saidv beam. about said predetermined path.

6. Anelectron` discharge device having means, including a., cathode, for directing an electron beam4 along a predetermined path, deflecting elec. trodes positioned alongl the path. of said electrons,- an output electrode meansfor receiving said e1ec. trons, means. for applying analternating voltage of a fundamental frequency to said deflecting electrodes for. deflecting said beam. of electrons about said predetermined path as a mean position,.said outputelectrode havingr means for gen. erating an output current of a harmonic frequency whenv said beam is` equally1 deflected about said mean. position and for generating an output. currenthaving av fundamental component when said beam is unequallydeflected about said mean position, means connected to the. output electrode and responsive to an output current having a fundamental frequency component for varying the applied voltage of fundamental frequency to said deecting electrodes for varying the output current, and means responsive to the variations of said output current for varying the bias on said deflecting electrodes for maintaining equal deflection of the electron beam on both sides of said predetermined path.

7. An electron discharge device having means including a cathode for directing a beam of elecplying an alternating potential of a fundamental frequency to said defiecting electrodes, said output electrode system generating an output current having a harmonic frequency of said fundamental frequency when said beam is properly centered along said predetermined path and generating an output current having a fundamental frequency output component when said beam is deflected unequally on opposite sides of said predetermined path, means for applying a biasing voltage to said deiiecting electrodes for maintaining said beam along said predetermined path when no deflect-ing voltage is applied to said deflec'ting electrodes, a phase responsive rectifier circuit associated with said biasing means, and means connected to said output electrode system and responsive to an output current having a fundamental frequency component for controlling, the phase responsive rectifier circuit for varying the relative biasing voltages on said deflecting electrodes.

8. An electron discharge device having means for directing an electron beamalong a predetermined path, deiiecting electrodes positioned along the path of said electrons, and output electrode means for receiving said electrons, means for applying an .alternating voltage of a fundamental frequency to said defiecting electrodes for rdeflecting said beam of electrons about said predetermined path as a mean position, said output electrode system having means for generating an output current having aharmonic frequency of said fundamental frequency when said beam is properly centered along said predetermined path and generating an output current having a fundamental frequency component when said beam is deflected unequally on opposite sides of said predetermined path, biasing means for applying a biasing voltage to said defiecting electrode, means connected to the output electrode means and including feedback means responsive to an output current of said fundamental frequency for varying the magnitude of the applied alternating voltage of fundamental frequency to said defiecting electrodes for varying the output current, and means responsive to the variations of said output current for varying the bias on said defiecting electrodes for maintaining equal deflection of the electron beam on both sides of said predetermined path. Y

' 9. An electron discharge device having a cathode for supplying a beam of electrons along a predetermined path, an output electrode positioned in the path of said electrons and a pair of defiecting electrodes positioned on opposite sides of said beam path and between said cathode and output electrode, and an intercepting electrode positioned between said cathode and output electrode and on which said beam is directed when no deflecting voltage is applied to said deiiecting electrodes, means for applying an alternating voltage of one frequency to said deflecting electrodes for defiecting said electron beam across saidV intercepting electrode whereby an output current fiows to said output electrode of a frequency twice that at said one frequency when said beam is properly centered but having a component of said fundamental frequency when said beam is off center, biasing means for applying a biasing voltage to said defiecting electrodes to maintain said beam directedA on said intercepting electrode when no alternating voltage is applied to said deflecting electrodes from said alternating voltage source, and means connected between said output electrode and said biasing means and responsive to an output current of said one frequency upon deviation of the electron beam from said predetermined path as'a mean position for returning said beam to said predetermined path as a mean position said last means including a phase responsive rectifier coupled to said biasing means for varying the biasing voltage applied by said biasing means to said deiiecting electrodes when said beam is unequally deflected about said predetermined path as a mean position.

10. An electron discharge device having means including a cathode means for directing electronsV along a predetermined path, an output electrode for receiving said electrons and an intercepting element positioned between said cathode and said a phase responsive rectifier for applying a voltage to said resistor and including a pair of electron discharge devices having cathodes, grids, and anodes. said anodes being connected to opposite ends of said resistor, said tuned circuit being coupled to said grids, the electron discharge device having defiecting electrodes generating an output current having a fundamental frequency component when said beam is off-center, said tuned circuit responding to said fundamental output current component when said beam is offcenter for causing one of said pair of electron discharge devices to conduct more current than the other for varying the biasing voltage on said resistor whereby the bias on said defiecting electrodes is varied to return said beam to a centered position. Y

11. An electron discharge device having means including a cathode means for directing electrons along a predetermined path, an output electrode for receiving said electrons, an interceptor element positioned between said cathode and said output electrode, deiiecting electrodes positioned along the path of said electrons and on opposite sides thereof, means for applying an alternating voltage of a fundamental frequency to said deflecting electrodes for periodically deflecting said` electron beam across said intercepting element, a circuit connected to said output electrode tuned to respond to an output current of the frequency of said alternating voltage, and biasing means connected between said deiiecting electrodes and including a resistor, a pair of electron discharge devices having cathodes, grids, and anodes, the said anodes being connected to opposite ends of said resistor, said tuned circuit including a transformer having a secondary the opposite ends of which are connected to said grids, and means for applying an alternating voltage between said cathodes and said anodes of the frequency of said alternating voltage applied to said deflecting electrodes, said electron discharge device having deflecting electrodes generating an output current having a fundamental frequency component when said beam is off-center, said transformer responding to said fundamental output current component for causing one of saidV pair of electron discharge devices tov conduct more current'- mrL; 44441;-

anaemia f3 than the. other for varying theY biasing voltage-v on said resistor.' Wherebythei bias on said dee'ct-V ing electrodes is varied toiV return said beam to a centered position.

12. An electron discharge device having; means including a cathode means for. directing electrons along a predeterminedI path, an output electrode for. receiving said electrons, an. interceptor element positioned between said cathode and said output electrode, deflecting electrodes positioned along the path of said electrons and on opposite sides thereof, means for applying an. alternating voltage. of a fundamental. frequency to saidl de*- flecting electrodes for periodically deflecting said electron beam across said intercepting; element to provide an output current having a second harmonic frequency, a circuit connected to' said output' electrode tuned to respond. to an output current of the fundamental frequency ofV said alternating voltage, and a phase responsive rectier biasing means connected with said deflect- -ing electrodes and including a pairy of electron discharge devices, said tuned circuit being coupled to said electron discharge devices forcontrol thereof, the electron discharge'device having deflecting electrodes generating an output current having a fundamental frequency component when said beam is oi-center, said tuned circuit responding to said fundamental output current component for causingl one of said electron discharge devicesV to conduct more current than the other for varying the biasing voltages on said d'eiiecting electrodesr to return said: beam to a centered position.

13. An electron. discharge device having; means including'a cathode means for directing electrons along a predetermined path,. an output electrode for receiving said electrons, an interceptor element positioned between said cathode and said output electrode, deflecting electrodesY positioned along the path of said' electronsV and on opposite sides thereof, means for applying an alternating voltage of a fundamental frequency to said deflecting electrodes for periodically deflecting said electron beam across said intercepting element to provide an output current having a second. harmonic frequency, a circuit connected to said output electrode tuned to respond to an output current of the fundamental frequency of said alternating voltage, and a rectifier biasing means connected with said deiiecting electrodesv and including an electron discharge device, said tuned circuit being coupled to saidelectron discharge device for control thereof, the electron discharge device having deflecting electrodes generating an output current having a fundamental frequency component when said beam is off-center, saidV tuned circuit responding to said fundamental output current component for causing said electron discharge device to conduct varying amounts of current for varying the biasing voltage on said deflecting electrodes to return said beam to a centered position.

14. An electron discharge device having' means including a cathode means for directing electrons along a predetermined path, an output' electrode for receiving said electrons, an interceptor element positioned between said cathode and said output electrode, deiiecting electrodes positioned along the path of said electrons and on opposite sides thereof, means for applying an' alternating voltage of a fundamental frequency to said deflecting electrodes for periodically defiecting said electron beam across said intercepting element. to provide an outputV current having a second harmonic frequency, ai circuit connected to: said outeputkelectrode tuned to respond to, an; outputicinrrent `of.v the fundamental frequency of said alter'- nating voltage, and biasing means connected be.- tween saiddeiiecting electrodes and: including: a. resistor, apair of electron discharge devices eachh having a cathode, grid, andA anode, theY said: anodes being. connected to opposite ends of said resistonsaidt tuned circuit being coupled to said2 grids, andimeans including a transformer having: a secondary the opposite ends of which; areY con-- nectecl to the cathodes of saidv pair of electronl discharge devices for applying an alternating; voltage between saidcathodes ofthe fundamentai frequency of said alternating voltage applied to'- sai'ddeecting electrodes', the electron discharge. device having d'eecting electrodes generating an output current having: a fundamental frequency component.' when said beam is off-center, said= tuned; circuit responding toV said fundamental'. frequency output, current componentA for' causing.v one of. said pair of electron discharge devices tol conduct morecurrentthan the other for' varying the.vl biasing; voltage on said resistor whereby the biason said d'eiiecting electrodes is varied to return said beam to a centered position.

15. An electron discharge device having means including a cathode means for directing electrons along' a predetermined path, an. output electrode for receiving said electrons, aninterceptor element positioned between said cathode and said output. electrode, deiiectingv electrodes positioned along' the path of said electrons and: on oppositeV sides thereof, means for applying an alternating" voltage of: a fundamental fre--4 quency to said deecting electrodes for' period-` ically deflecting said' electron beam across sai'd intercepting element to provide an output cur--n rent having a second harmonic frequency, a circuit connected, to said output electrode tunedl to respondv to an output current of the fundamental frequency of said alternating voltage, and biasing means connected between said deflecting electrodes and including a resistor, a pair of electron discharge devices each having a cathode, grid, and ano-de, the said anodes being con# nected to. opposite ends of said resistor, saidtuned' circuit being coupled: to' said grids, and means for applying an alternating voltage. of'V said: funda'- mental frequency betweenv said cathodes and in cluding an. inductance; and a feedback:A coil connected between each anode of sai-d pair of electron discharge devices and said resistor and coupled to said inductance, the electron discharge device having deflecting electrodesv generating: an output current having a fundamental frequency component when said beam isv off-center', said tuned circuit responding to said output current component of fundamental frequency for causing one of said pair of electron discharge de,- vices to conduct more current than. the other for varying the biasing voltage on said resistor whereby the biasr on said delecting electrodes is varied to return said beam to a centered position;

16. An electron discharge device having means` including a cathode means for directing electrons. along a predetermined path, an output electrode for receiving said electrons, anv interceptor element positioned between said cathode and said output electrode, deecting electrodes positioned along the path of said electrons and on opposite sides thereof, means for applying an alternating voltage of a fundamental frequency to said deflecting electrodes for periodically del ecting said' electron beam across said intercepting elementto provide an output current having a Second harmonic frequency, a circuit connected to said output electrode tuned to respond to an. output current of the fundamental frequency-of vsaid alternating voltage, and biasing means connected between said deecting electrodes and including a resistor, a second resistor connected between said first resistor and said cathode means, a second electron discharge device having a cathode, grid, and anode, said anode being connected to one end of said first resistor,.said,tuned circuit being coupled to said grid, and means for applying an .alternating voltage between the cathode and the anode of said second electron discharge device of the frequency of said alternating voltage applied to said deecting electrodes, the electron discharge device having deflecting electrodes generating an output current having a fundamental .frequency componentY when said beam is off-center, said tuned circuit responding to said output current component of fundamental frequency for causing said second electron discharge device to conduct varying amounts of currents for varying the biasing voltage on said resistor whereby the bias onv said deilecting electrodes is varied to return said beam to a centered position. 4

1'7. A method of maintaining a beam of electrons centered in a beam deflection tube comprising applying an alternating deflecting voltage to said beam for causing said beam to be deflected periodically and equally on both sides of a predetermined mean path, causing said beam to generate an output current having a harmonic frequency of said deiiecting voltage when said beam is properly centered and an output current component having a frequency corresponding to the frequency of said deflecting voltage when said beam is unequally deflected about said mean path, rectifying said output current of fundamental frequency, and utilizing said rectified current for providing a voltage bias for shifting said beam when said beam is off-center to maintain equal deflection of said beam about said. predetermined path as a mean position.

I8. The method of maintaining an electron beam in a beam tube centered along a predetermined path as a mean position in an electron discharge device having a transconductance characteristic passing successively through negative and positive values, comprising applying an alternating electric field to said beam for periodically deflecting said beam about said predetermined path, generating an output current having a frequency corresponding to a harmonic frequency of said deflecting voltage when said beam is properly centered land generating an output current component having a frequency corresponding to the frequency of said alternating electric field When said beam is off-center, said transconductance characteristic having a positive or negative value depending upon the phase relationship of said H output current of fundamental frequency Awith respect to the phase of said alternating electric field, rectifying said output current of fundamental frequency for generating a biasing voltage, and applying said biasing voltage to said electron beam for returning said beam to a properly centered position.

19. The method of maintaining an electron beam centered along a predetermined path as a mean position in an electron discharge device provided with a source of electrons, a control electrode means and an output electrode and having a transconductance characteristic passing successivelyvthrough negative and positive values whereby the output current experiences a reversal of slope, and comprising the steps of applying biasing voltages to said electron discharge device for adjusting thedevice to a point of zero transconductance such that with varying' voltages applied to said control electrode means the transconductance will vary periodically between equal negative and positive values when said beam is properly centered, said transccnductance having higher positive values than negative values When said beam is off-center in cne'direction and having greater negative values than positive values when the beam is off-center in the other direction whereby an output current component having a frequency of the applied varying voltage is generated when said beam is off-center, rectifying said output current component for generating a biasing voltage and applying said biasing voltage to the control electrode means for returning said beam to a properly centered position.

20. The method of maintaining an electron beam centered along a predetermined path as a mean position in an electron discharge device provided with a source of electrons, a control electrode means and an output electrode and having an output current characteristic which increases on either side of a minimum value whereby the output current experiences a reversal of slope, and comprising the steps of applying biasing voltages to said electron discharge device for adjusting the device to a point of minimum current such that with varying voltages applied to said control electrode means the output current will increase equally on both sides of said minimum current when said beam is properly centered,

said output current having a higher value on one side than on the other of said minimum when said beam is off-center, whereby an output current component having a frequency of the applied varying voltage is vgenerated when said beam is off-center, rectifying said output current component for generating a biasing voltage, and applying said biasing voltage to the control electrode means for returning said beam to a properly centered position.

2l. An electron discharge device having means including a cathode for directing a beam of electrons along a predetermined path, an output electrode system in the path of said beam of electrons, and means positioned along the path of said electrons between said cathode and said output electrode system for deflecting said beam of electrons, means for applying an alternating voltage of a fundamental frequency to said deflecting means, said output electrode system generating an output current having a harmonic frequency of said fundamental frequency when said beam is properly centered along said predetermined path and generating an output current having a 'fundamental frequency component when said beam is deflected unequally on opposite sides of said predetermined path, means including aj phase-responsive rectier for applying a biasing voltage to said reflecting means for maintaining said beam centered along said predetermined path and means coupled to said output electrode system and responsive to an output current having a fundamental frequency component for control- .ling the phase-responsive rectifier circuit, the

means coupled to said output electrode system having an output of one phase when said beam is off-center in one direction and having an output of an opposite. phase when the beam is oiufcenter in the other direction, said phase-respon-l sive rectier varying the bias voltage in one direction to return said beam to a centered position in response to one phase and varying the bias voltage in the opposite direction when the phase is opposite.

22. An electron discharge device having means including a cathode for directing an electron beam along a predetermined path, electrode means in the path of said electrons, and defiecting electrode means along the path of said electrons between said cathode and the electrode means in the path of said electrons, means for applying a biasing voltage on said deflecting electrode means, means for maintaining said beam directed along said predetermined path when no deiiecting voltage is applied to said beam is oi-center in the opposite direction, and means responsive to the diierence in values of said transconductance due to deviation of said beam from said path for varying the voltage applied by said biasing means in one direction when said beam is off-center in one direction and varying the voltage applied by said biasing means in the opposite direction when said beam is oli-center in the opposite direction.

EDWARD W. HEROLD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,096,653 Soller Oct. 19, 1937 2,165,308 Skellett July 11, 1939 2,190,069 Hollmann Feb. 13, 1940 2,225,330 Cage Dec. 17, 1940 2,287,296 Dallos June 23, 1942 2,294,659 Herold Sept. 1, 1942 2,305,617 Hansell Dec. 22, 1942 2,313,886 Nagy et al. Mar. 16, 1943 2,357,922 Ziebolz et al Sept. 12, 1944 2,370,255 Nagy et a1. f Feb. 27, 1945 2,383,758 Ziebotz Aug. 28, 1945 2,390,250 Hansell Dec. 4, 1945 2,411,605 Webb Nov. 26, 1946 

